-Event: The heroku command is not recognized by
$ heroku create
-Solution: In toy_app, I started over from the heroku installation of "1.5.1 Heroku setup".
-Note: Is it necessary to install for each app? Confirmation required
･ Progress: Chapter 2 2.1.1 ~ 2.2.1 Completed
-Impression: When you type a command to terminal, you should always be aware that the current directory is important.